Guyed Towers

When the tower is very high, it is sometimes desirable to maintain stability by means of guy wires rather than a large foundation. Although it is not uncommon to find two or even three sets of guy wires on one stack, towers seldom have more than one set, and even these are rare. This discussion, therefore, will be confined to towers with one set of guy wires. 

Four guy wires are usually used for each set, although in some instances three, and in others as many as six have been used. They are attached to a rigid collar which is located at a point approximately 2/3 (sometimes 3/4) of the tower height above the foundation. 

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Properly designed process equipment, taking Into account all the marine vessel motions, Is essential to ensure process quality specifications are met and onstream time 1s maximized. The motions of tankers and semisubmerslbles are most severe and consequently the design of the process equipment for these applications has received the most attention. However, the technology can be utilized to Improve the performance of process equipment on structures such as guyed towers and tension leg platforms which only move 1n one plane and generally with lower amplitudes. 

Two tower types will be porting and guyed towers. 

It was shown by equation (11-1) that the total soil loading, to be considered in the design of tower foundations, is the sum of Si, the dead load, and S2, the load caused by the overturning or wind moment. There is no overturning moment on guyed towers however, the wind pressure does have an important effect on the foundation, as the soil is required to resist the vertical component of the pull on the guy wires. 

For guyed towers, therefore, equation (11-1) must be revised as follows ... 

Foundation bolts for guyed towers are required to resist the shearing action of the wind pressure at the base of the tower. It is obvious that ample allowance should be made in the size of the bolts to provide for the initial tension caused by tightening the nuts and for corrosion. 

The wind pressure acting on a guyed tower produces a negative bending moment at the collar and a positive bending moment between the base and the collar. The maximum values of these two moments can be calculated as follows ... 

For guyed towers, or stacks, the shear load from the overturning moment, S5, does not apply, but is replaced by... 

To determine potential wind sources for wind farms in New Mexico and South Dakota, USA, two 82 m carbon fiber RP meteorological measurement towers are to be used. These guyed towers, built by IsoTruss Structures of Brigham City, Utah, USA, will measure wind resources at the hub height of a number of large, megawatt-size wind turbines. Compared with the steel towers often used, the carbon fiber structure is easier to transport and can be delivered and assembled at a significantly lower cost. 

Examples of marine foundation types—(d) typical tension leg structure and (e) guyed tower structure. (From Gibson, R.E. and Dowse, B.E.W., Canadian Geotech. /, 18 171-178,1981. Reprinted with permission of Canadian Geotechnical Journal.)... 

FIGURE 10.235 Ground-conductor dressing for the base of a guyed tower. (After [9].)... 

The corrosion of guyed tower anchors such as shown in Fig. 7.13 and Fig. 7.14 and which is becoming an issue of critical importance will be used in the next sections to illustrate some of these corrosion cells. In many cases, the loss of one anchor to corrosion (Fig. 7.15) has resulted in the catastrophic loss of the supported communication tower (Fig. 7.16). 

The screw-in, auger, or helical anchor uses one or more single-turn helical plates attached to a rigid shaft to screw itself into the soil. This anchor system was developed for use on land to anchor guy wires for towers and poles. It has had limited use on the seabed to anchor pipelines and cables. Anchor penetration is dependent upon reaction force and torque from the drive unit in addition to soil strength. 

Towers shaii be anchored to the structure at intervals not exceeding 25 feet. In addition to tie-ins, a series of guys shall be installed. Where tie-ins are not practical the tower shall be anchored by means of guys made of wire rope at least one-half inch in diameter, securely fastened to anchorage to ensure stability. 

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